Is It not Time to Go back to Tamman’s Tg?

Abstract

Based on the analysis of numerous experimental data, it is shown that the currently generally accepted glass transition temperature Tg is not correct. It was the result of borrowing from G. Tamman the symbol Tg, which corresponds to the temperature at which a liquid in a viscous flow is transformed into a solid brittle glassy state, and using it instead of the symbol Tw. The latter corresponded to the bending temperature (for Tamman) on the property–temperature curve of glass-forming substances lying above Tamman’s Tg. The disclosed physico-chemical nature of the temperature curve Tw (currently, generally taken to be Tg), which is the temperature of the reverse direction of the interconversion of nanofragment patterns (of polymorphs) of the high- and low-temperature polymorphs that coexist in a vitreous substance, is based on the application of polymer-polymorphing representations of the structure of glass-forming substances. In the past few decades, the discovery of the preendothermal effect located, just as Tamman’s Tg, below the standard Tg, confirms the correctness of Tamman’s Tg characterized by the increased specific heat of the heated glass.